ABSTRACT. Antiostelma (Asclepiadaceae), previously recognized as a section of Hoya, is raised to generic rank. The new combinations Antiostelma lantsangense (Tsiang & P. T. Li) P. T. Li and A. manipurense (D. B. Deb) P. T. Li are proposed.

As a result of recent study of Chinese material of Asclepiadaceae and Apocynaceae from the Missouri Botanical Garden, the Smithsonian Institution, Harvard University, and the California Academy of Sciences, and during preparation of the accounts of these families for the Flora of China, it became evident that the delimitation of certain genera needed critical study, and several nomenclatural adjustments needed to be made. This publication deals with a new genus of Asclepiadaceae, Antiostelma. It was originally described as a monotypic section of Hoya R. Br. The new combinations are proposed in order to make the names available for the Flora of China and other floristic works in progress.

Antiostelma (Tsiang & P. T. Li) P. T. Li, comb. et stat. nov. Basionym: Hoya sect. Antiostelma Tsiang & P. T. Li, Acta Phytotax. Sin. 12: 126. 1974. TYPE: Antiostelma lantsangensis (Tsiang & P. T. Li) P. T. Li.

Lacticiferous epiphytic subshrubs. Leaves opposite, obdeltoid or obovate. Cymes extra-axillary, umbellate, subsessile or sessile. Calyx eglandular inside; corolla cylindric, lobes erect, aestivation twisted leftward; corona lobes 5, fleshy, erect, quadrate, adnate adaxially to gynostegium, bilateral margin manifestly recurved at back; stamens 5, anthers erect, with acuminate apical membranes; pollinia subquadrate, basal margin translucent; ovaries free; style apex beaked, exceeding apical membrane of anthers. Follicles linear-lanceolate. Seeds comose.

Antiostelma includes two species, A. lantsangensis and A. manipurense, that are endemic to China and India, respectively. The genus was originally recognized as a section of Hoya R. Br. (Tsiang & Li, 1974, 1977), but critical examination of several collections reveal that it is best treated as an independent genus readily distinguished from Hoya and Dischidia by the several characters summarized in Table 1.

The two species of Antiostelma are easily distinguished by the following key.

1a. Branches and leaves glabrous; leaf apex retuse; China ................................ A. lantsangense

1b. Branches and leaves densely pubescent; leaf apex truncate; India .............. A. manipurense

Antiostelma lantsangense (Tsiang & P. T. Li) P. T. Li, comb. nov. Basionym: Hoya lantsangensis Tsiang & P. T. Li, Acta Phytotax. Sin. 12: 126. 1974. TYPE: China. Yunnan: Mo-Jiang, 1,000 m, A. Henry 13689 (holotype, NY; isotype, IBSC).

Antiostelma manipurense (D. B. Deb) P. T. Li, comb. nov. Basionym: Hoya manipurensis D. B. Deb, J. Indian Bot. Soc. 34: 50. 1955. TYPE: India. Manipur, Litan, 1 Sep. 1953, D. B. Deb 1081 (holotype, CAL).

Acknowledgments. I am grateful to Peter H. Raven, William Tai, W. Douglas Stevens, Laurence Skog, Dan Nicholson, and David Boufford for their support of my visit to the United States. I am also grateful to Ihsan Al-Shehbaz for help with the manuscript.

Literature Cited

Tsiang, Y. & P. T. Li. 1974. Praecursers Flora Asclepiadacearum Sinensium. Acta Phytotax. Sin. 12: 79--149.

Tsiang, Y. & P. T. Li. 1977. Asclepiadaceae. Flora Reipublicae Popularis Sinicae 63: 475--559.